1. Field of the Invention
The present invention relates generally to barrier layers within integrated circuits. More particularly, the present invention relates to composite barrier layers within integrated circuits.
2. Description of the Related Art
Integrated circuits are formed from semiconductor substrates within and upon whose surfaces are formed resistors, transistors, diodes and other electrical circuit elements. The electrical circuit elements are connected internally and externally to the semiconductor substrate upon which they are formed through patterned conductor layers which are separated by dielectric layers.
In the process of forming within integrated circuits patterned conductor layers for connecting and interconnecting electrical circuit elements formed within and upon semiconductor substrates, it is common in the art to employ a barrier layer formed interposed between an electrode contact of an electrical circuit element and a conductor layer, typically an aluminum containing conductor layer, desired to be formed contacting the electrode contact of the electrical circuit element. Such barrier layers provide a barrier to: (1) inhomogeneous inter-diffusion of the electrode contact with the conductor layer; and/or (2) spiking of the conductor layer (when the conductor layer is formed from an aluminum containing conductor material) into the electrode contact. When an electrode contact is formed from a silicon containing material to yield a silicon containing electrode contact, as is most common in the art, there is typically also employed a metal silicide layer formed upon the electrode contact, typically through annealing a metal silicide forming metal layer in contact with the silicon containing electrode contact, in order to provide a low resistance connection to the electrical circuit element.
A typical electrical circuit element electrode contact employing such a barrier layer and a metal silicide layer (formed from a metal silicide forming metal layer) is illustrated by the schematic cross-sectional diagram of FIG. 1. Shown in FIG. 1 is a silicon semiconductor substrate 10 having formed upon its surface a pair of patterned dielectric layers 12a and 12b which define a window accessing the silicon semiconductor substrate 10. Formed through partial consumption of a blanket metal silicide forming metal layer (not shown) formed in contact with the portion of the silicon semiconductor substrate 10 exposed within the window is a metal silicide layer 14, along with a pair of metal silicide forming metal layer residues 16a and 16b. There is also shown formed upon the metal silicide forming metal layer residues 16a and 16b, and the metal silicide layer 14, a blanket barrier layer 18. Finally, there is shown in FIG. 1 a blanket conductor layer 20 formed upon the blanket barrier layer 18, where the blanket conductor layer 20 has formed thereupon a patterned photoresist layer 21. Within the electrical circuit element electrode contact structure whose schematic cross-sectional diagram is illustrated in FIG. 1, the metal silicide layer 14 is typically, although not exclusively, a titanium silicide layer, while the metal silicide forming metal layer residues 16a and 16b are thus typically, although not exclusively, titanium metal layer residues. In addition, the blanket barrier layer 18 is typically a blanket titanium-tungsten alloy barrier layer since titanium-tungsten alloy barrier layers typically have superior step coverage within narrow high aspect ratio apertures. Further, as is most common in the art, the blanket conductor layer 20 is typically a blanket aluminum containing conductor layer. Finally, the patterned photoresist layer 21 is formed of a photoresist material which is susceptible to stripping within a photoresist stripping/polymer removal composition which employs a hydroxyl/amine compound such as but not limited to hydroxylamine (ie: NH2OH; (HDA)) and bis (2-aminoethoxy)-2-ethanol (ie: (NH2CH2CH2O)2CHCH2OH; (DGA)).
While the electrical circuit element electrode contact structure whose schematic cross-sectional diagram is illustrated in FIG. 1 has become quite common in the art of integrated circuit fabrication, the electrical circuit element electrode contact structure whose schematic cross-sectional diagram is illustrated in FIG. 1 is not entirely without problems. In particular, when patterning the electrical circuit element electrode contact structure whose schematic cross-sectional diagram is illustrated in FIG. 1 to form a patterned electrical circuit element electrode contact structure there is often observed partial delamination of a patterned barrier layer from the patterned dielectric layers 12a and 12b when the metal silicide forming metal layer residues 16a and 16b are formed of titanium. A schematic cross-sectional diagram illustrating the mechanism through which such partial delamination occurs is illustrated in FIG. 2.
Shown in FIG. 2 is a patterned conductor layer 20xe2x80x2 formed upon a patterned barrier layer 18xe2x80x2, where the patterned conductor layer 20xe2x80x2 is patterned from the blanket conductor layer 20 and the patterned barrier layer 18xe2x80x2 is successively patterned from the blanket barrier layer 18. Also shown in FIG. 2 is a pair of voids 22 where the patterned barrier layer 18xe2x80x2 and the patterned conductor layer 20xe2x80x2 have delaminated from the patterned dielectric layers 12a and 12b. Such delamination typically occurs due to etching and undercutting of a pair of patterned metal silicide forming metal layer residues formed of titanium (not shown) successively patterned from the metal silicide forming metal layer residues 16a and 16b, where the etching and undercutting occurs due to contact of the patterned metal silicide forming metal layer residues with a stripping composition employed in removing from the surface of the electrode contact structure whose schematic cross-sectional diagram is illustrated in FIG. 2 a patterned photoresist layer employed in defining the patterned conductor layer 20xe2x80x2, the patterned barrier layer 18xe2x80x2 and the patterned metal silicide forming metal layer residues. In particular, when the metal silicide forming metal layer residues 16a and 16b are formed of titanium, photoresist stripping/polymer removal compositions which employ hydroxyl/amine compounds such as but not limited to hydroxylamine (ie: NH2OH; (HDA)) and bis (2-aminoethoxy-2-ethanol) (ie: (N2CH2CH2O)2CHCH2OH; (DGA)) may be particularly efficient in etching patterned titanium metal silicide forming metal layers residues to provide the undercutting and void 22 formation as illustrated in FIG. 2.
It is therefore desirable in the art to provide methods for forming electrical circuit element contact structures such that the contact structures are not susceptible to delamination from surfaces of substrates upon which are formed those contact structures, due to etching with stripper solutions of metal silicide forming metal layers formed within those structures, that the present invention is generally directed.
Novel barrier layer constructions which provide improved properties to integrated circuits are know within the art of integrated circuit fabrication. For example, Ngan et al. in U.S. Pat. No. 5,378,660 and U.S. Pat. No. 5,504,043 disclose a titanium nitride barrier layer construction with improved diffusion barrier properties for aluminum layers formed at elevated temperatures upon the titanium nitride barrier layer construction. The titanium nitride barrier layer within the titanium nitride barrier layer construction has incorporated therein additional oxygen. In addition, Wang et al., in U.S. Pat. No. 5,508,212 disclose a large tilt angle method for forming a titanium nitride layer which limits encroaching of titanium silicide layers within a field effect transistor within an integrated circuit.
Desirable in the art are additional methods for forming barrier layers within integrated circuits. Particularly desirable are additional methods through which there may be formed barrier layers upon low contact resistance metal silicide layers within integrated circuits, where a metal silicide forming metal layer residue, most preferably a titanium layer residue, formed beneath the barrier layer is not susceptible to dissolution, thus yielding delamination of the barrier layer from an electrode contact within the integrated circuit. It is towards these goals that the present invention is more specifically directed.
A first object of the present invention is to provide a barrier layer for use upon an electrode contact within an integrated circuit.
A second object of the present invention is to provide a barrier layer in accord with the first object of the present invention, where the barrier layer when formed upon a low contact resistance metal silicide layer formed upon the electrode contact has limited susceptibility to delamination due to dissolution of metal silicide forming metal layer residues formed beneath the barrier layer.
In accord with the objects of the present invention, there is provided a barrier layer for use upon an electrode contact within an integrated circuit. To form the barrier layer of the present invention, there is first provided a silicon substrate layer having an electrode contact region formed within the silicon substrate layer. There is then formed over the silicon substrate layer a titanium layer, where the titanium layer contacts the electrode contact region of the silicon substrate layer. The titanium layer is then processed thermally in a nitrogen containing atmosphere to form a titanium silicide layer in contact with the electrode contact region and a titanium nitride layer formed thereover. The titanium layer is completely consumed informing the titanium silicide layer and the titanium nitride layer. Finally, there is formed upon the titanium nitride layer a barrier layer.
There is provided by the present invention a barrier layer for use as an electrode contact within an integrated circuit, where the barrier layer when formed upon a low contact resistance metal silicide layer has limited susceptibility to delamination due to dissolution of metal silicide forming metal layer residues formed beneath the barrier layer. The barrier layer formed through the method of the present invention has limited susceptibility to delamination since the titanium layer employed in forming a titanium silicide layer upon an electrode contact beneath the barrier layer is completely consumed in forming either the titanium silicide layer or a titanium nitride layer. Since there remains no titanium metal which may be undercut beneath the barrier layer, the barrier layer has limited susceptibility to delamination.